Injection Device

ABSTRACT

The application concerns an injection device for apportioning set doses of a drug from a reservoir ( 40 ) to a subject. The injection device comprises a housing having an interior thread ( 101,112 ) formed as an outwardly pointing thread ( 101,112 ) carried on an upstanding tower centrally located in the pen shaped device. This outwardly pointing thread ( 101,112 ) forms a first thread connection with the interior thread of the rotatable scale drum ( 90 ). The injection device further comprises a driver ( 70 ) for moving the piston rod ( 120 ) forward when moved axially. The driver ( 70 ) operates the piston rod ( 120 ) through a second thread connection having a pitch different than the first thread connection.

THE TECHNICAL FIELD OF THE INVENTION

The invention relates to an apparatus such as an injection pen fordelivering a drug to the human body preferably in a subcutaneous way andespecially to a user energized injection pen having a rotatable scaledrum.

DESCRIPTION OF RELATED ART

In the disclosure of the present invention reference is mainly made tothe treatment of diabetes by injection of insulin; however this is onlyan exemplary use of the present invention.

Injection pens are mainly made for users who have to inject themselvesfrequently, e.g. people suffering from diabetes. A number of demands areset to such injection pens. The setting of a dose must be easy anunambiguous and it must be easy to read the set dose. It must bepossible with a minimum of trouble to cancel or change a wrongly setdose and when the dose is injected the dose setting must return to zero.When a prefilled injection pen is in question, i.e. an injection penwhich is disposed of when the reservoir is empty, the injection pen mustfurther be cheap and made of materials suitable for recycling.

Most dose setting devices work with a threaded piston rod co-operatingwith a nut where the nut and the piston rod may be rotated relative toeach other. The dose setting may be obtained by screwing the nut awayfrom a stop to which it is return during injection by pressing thepiston rod forward until the nut member abuts the stop. By other dosesetting devices one of the elements, the nut or the piston rod, is keptinrotatable and the other is allowed to rotate a set angle depending onthe set dose, whereby the piston rod is screwed forward a distancethrough the nut member.

A prior art delivery apparatus is disclosed in U.S. Pat. No. 6,004,297.The apparatus disclosed in FIG. 6 to 10 comprises a scale drum having anexterior thread which is guided in a helical thread provided on theinside of the outer wall of the housing. The scale drum is axiallycoupled to the driver to follow the axial movement of the driver. Thedriver further has an interior thread which engages a proximal thread onthe piston rod such that when the driver is moved axially forward in thepen, the piston rod is rotated and henceforth screwed forward in thethread connection between the piston rod and the wall of the housing.

The tolerances in the thread connection between the scale drum and thehousing is decisive for the precision of the display. If the scale drume.g. were a little loose in the thread connection an erroneous dose sizecould be displayed, however if it were too tight in the threadconnection, it would be difficult to press back the dose setting knob.

A similar injection pen is disclosed in WO 04/078241. This injection pencomprises a threaded piston rod which is screwed forward in an internalthreaded nut when rotated. A drive sleeve having a thread mating thethread of the piston rod rotates the piston rod when moved axiallyforward. The drive sleeve is releasable coupled to a dose dial sleevewhich is rotated to dial up a dose. The dose dial sleeve is rotated outfrom the housing in order to set up a dose and it is rotated back torelease the set dose. The drive sleeve is rotated together with the dosedial sleeve when a dose is set but prevented from rotation when the setdose is injected. When the dose dial sleeve is rotated back, the usermust be sure that the dose dial sleeve is free to rotate as any obstaclefor the rotation will increase the pressure needed to press back thedose dial sleeve.

Some drugs, such as insulin are self-administered, and the typicaldiabetes person will require subcutaneous injections of insulin severaltimes during the course of the day. In administering such an injection,the user, once the size of the dose has been set holds the injection penin the palm of one hand while placing the thumb finger on the back-endof the push button. When a large dose has been set, the distance fromthe device itself to the push button is considerable thereby making itdifficult for people with small hands or reduced dexterity to reachbehind the push button.

Since most injections of these drugs are performed in privatesurroundings by the user himself there is a great desire for very simpleyet also very precise injection devices having a very precise dosereading combined with a small displacement of the push button even whensetting large doses.

DESCRIPTION OF THE INVENTION

Having regard to the above-identified prior art devices, it is an objectof the present invention to provide a drug delivery device whicheliminates disadvantages in the prior art drug delivery device. It isespecially an object to provide a drug delivery device having a reduceddisplacement of the push button and a reduced friction making the drugdelivery device more user friendly. Further it is an object to providean injection device were all rotating parts are encapsulated.

Claim 1:

By surrounding the dose indication sleeve with a shield, it is securedthat the user does not touch the scale drum during operation. In anydevice, the scale drum must be rotatable in order to display the setdose. When the scale drum is encapsulated inside a shield which at thesame time can be used to transfer pressure from the injection button,the injection device can be made considerable shorter than known deviceswere the dose drum is encapsulated in the housing of the injectiondevice. In order for a user to visible see the scale indication drum,the shield must be made such that the user can view the scale drum e.g.by providing a longitudinal opening in the shield which opening isaligned with the window in the housing of the injection device.

Claim 2:

The shield could alternatively be made with a longitudinal transparentarea through which transparent area the indications on the scale drumcan be viewed. The shield could also be made fully transparent which ispreferred if the shield rotates. The transparent or partly transparentshield can be made cylinder-shaped to surround the scale drum, or atleast a part of the scale drum. This allows the scale drum to climb outof the housing yet being untouchable.

Claim 3-5:

The drive sleeve is in an exemplary embodiment able to be coupled anduncoupled from the shield. If the dose setting and injection mechanismis the kind were the driver during injection is brought axially back toits initiate position in order to force the piston rod to rotate, thedriver can be rotational locked to the shield during injection such thatboth the shield and the driver is moved axially. This permits the scaledrum to rotate back to its initiate position inside the shield withoutbeing touched by the user.

The shield is either axially guided in the housing or free to rotaterelative to the housing. If the shield is free to rotate it canpreferable be rotational locked e.g. by moulding to the push button soas to form one common dose setting member. If the shield is axiallyguided in the housing the preferred way is to guide the shield in alongitudinal track in the housing.

Claim 6:

Correspondingly, an injection device is provided where the drive sleeveis associated with a first thread and releasable connected to the dosesetting member such that the drive sleeve can be connected ordisconnected from the dose setting member.

Further, the dose indication sleeve is associated with a second threadhaving a pitch different from the first thread and releasable connectedto the dose setting member such that the dose indication sleeve can beconnected or disconnected from the dose indication sleeve.

This results in the four following different engagements:

-   -   Dose setting member connected to both drive sleeve and dose        indication sleeve,    -   Dose setting member disconnected from both drive sleeve and dose        indication sleeve,    -   Dose setting member connected to the drive sleeve but        disconnected from the dose indication sleeve,    -   Dose setting member disconnected from the drive sleeve but        connected to the dose indication sleeve.

During dose setting, one engagement can be utilized while duringexpelling of the dose a different engagement can be utilized.

At the same time, the drive sleeve can be guided in one threadconnection having one pitch and the dose indication sleeve in adifferent thread connection having a different pith such that the drivesleeve and the dose indication sleeve can be rotated with differentrotational speeds.

Claim 7:

When setting a dose the dose setting member is disconnected from thedrive sleeve and connected to the dose indication sleeve such that whenrotating the dose setting member, the dose indication sleeve is screwedup the second thread at a speed determined by the pitch of the secondthread.

If the drive sleeve is axially coupled to the dose setting member andthe dose indication sleeve it will be dragged along and forced to rotatein the first thread at a speed determined by pitch of the first speed.

When injecting or otherwise expelling the set dose, the dose settingmember is connected to the drive member and disconnected from doseindication sleeve such that an axial pressure applied to the dosesetting member will be transformed to an axial movement of drive sleevewhile the disconnected dose indication scale will be screwed back in thesecond thread.

Claim 8:

The pitch of the first thread is decisive for ratio of the translationof the longitudinal movement of the drive sleeve to the rotationalmovement of the piston rod, and the pitch of the second thread isdecisive for the ratio of the translation of the longitudinal movementof the dose indication sleeve and the rotational movement of the doseindication sleeve.

According to an example of the invention, the first thread has a pitchlarger than the pitch of the second thread. A result of this is that thedose indication sleeve rotates more than one revolution for eachrevolution the drive sleeve is rotated.

When setting a dose the dose indication member and the dose settingmember is screwed up the second thread having the smaller pitch suchthat the distance the dose setting member grows out from the proximalend of the injection device for each dose indication printed on the doseindication sleeve is reduced.

Claim 9-11:

During injection the drive sleeve must be moved axially with out anyrotation in order to make sure the set dose is correctly expelled.

This can be accomplished by preventing the drive sleeve from rotatingrelatively to the housing.

A preferred way of doing is by locking the drive shield to a shieldwhich is guided in a longitudinal track in the housing.

Since the shield is located on the outside of scale indication sleeve itshould be at least partly transparent such that the user can view thedose indication sleeve through the shield.

Further the axially movable shield prevents the user from physicalcontact with the rotating scale indication sleeve.

Claim 12:

When setting up a dose to be expelled, the dose setting member isrotational connected to the dose indication sleeve. The drive sleevewhich is disconnected from the dose setting member is supported by thedose indication sleeve such that it follows the axial movement of thedose setting member and the dose indication sleeve. By doing so thedrive sleeve is screwed up its thread connection.

Claim 13-14: The thread in which the drive sleeve engages is the firstthread which is provided on the piston rod guide which again is keyed tothe piston rod such that the piston rod rotates with the piston rodguide.

In an alternative embodiment, the drive sleeve can engage directly in athread provided on the piston rod.

Claim 15:

The second thread which is engaged by the dose indication sleeve isprovided on a thread tower which is centrally provided in the housing.This thread tower can either be a loose insert which is rotationalconnected to housing or it can be moulded integrally with the housing.

DEFINITIONS

An “injection pen” as in this application is typically a mechanical i.e.user energized injection apparatus having an oblong or elongated shapesomewhat like a pen for writing. Although such pens usually have atubular cross-section, they could easily have a different cross-sectionsuch as triangular, rectangular or square.

As used herein, the term “drug” is meant to encompass anydrug-containing flowable medicine capable of being passed through adelivery means such as a hollow needle in a controlled manner, such as aliquid, solution, gel or fine suspension. Representative drugs includespharmaceuticals such as peptides, proteins (e.g. insulin, insulinanalogues and C-peptide), and hormones, biologically derived or activeagents, hormonal and gene based agents, nutritional formulas and othersubstances in both solid (dispensed) or liquid form.

Correspondingly, the term “subcutaneous” injection is meant to encompassany method of transcutaneous delivery to a subject.

Further the term “injection needle” defines a piercing member adapted topenetrate the skin of a subject for the purpose of delivering orremoving a liquid.

All references, including publications, patent applications, andpatents, cited herein are incorporated by reference in their entiretyand to the same extent as if each reference were individually andspecifically indicated to be incorporated by reference and were setforth in its entirety herein.

All headings and sub-headings are used herein for convenience only andshould not be constructed as limiting the invention in any way.

The use of any and all examples, or exemplary language (e.g. such as)provided herein, is intended merely to better illuminate the inventionand does not pose a limitation on the scope of the invention unlessotherwise claimed. No language in the specification should be construedas indicating any non-claimed element as essential to the practice ofthe invention. The citation and incorporation of patent documents hereinis done for convenience only and does not reflect any view of thevalidity, patentability, and/or enforceability of such patent documents.

This invention includes all modifications and equivalents of the subjectmatter recited in the claims appended hereto as permitted by applicablelaw.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be explained more fully below in connection with apreferred embodiment and with reference to the drawings in which:

FIG. 1 shows a perspective view of the injection device.

FIG. 2 shows a sectional view of the injection device of FIG. 1 with nodose set.

FIG. 3 shows a sectional view of the injection device of FIG. 1 with adose set.

FIG. 4 shows a partly exploded view of the injection device.

FIG. 5 shows a perspective view of the parts presented in FIG. 4.

FIG. 6 shows a perspective view of a different example of an injectiondevice.

FIG. 7 shows a sectional view of the injection device of FIG. 6 with nodose set

FIG. 8 shows a sectional view of the injection device of FIG. 6 with adose set

FIG. 9 shows a perspective view of another example of an injectiondevice.

FIG. 10 shows a sectional view of the injection device of FIG. 9 with nodose set

FIG. 11 shows a sectional view of the injection device of FIG. 9 with adose set

FIG. 12 shows a perspective view of another example of an injectiondevice.

FIG. 13 shows a sectional view of the injection device of FIG. 13.

FIG. 14 shows a perspective view of an embodiment of the injectiondevice disclosed in FIG. 12 and 13.

FIG. 15 shows a perspective view of another example of an injectiondevice.

FIG. 16 shows a perspective view of the injection device according toFIG. 16

FIG. 17 shows a perspective view of an embodiment of the injectiondevice disclosed in FIG. 15 and 16.

The figures are schematic and simplified for clarity, and they just showdetails, which are essential to the understanding of the invention,while other details are left out. Throughout, the same referencenumerals are used for identical or corresponding parts.

DETAILED DESCRIPTION OF EMBODIMENT

When in the following terms as “upper” and “lower”, “right” and “left”,“horizontal” and “vertical”, “clockwise” and “counter clockwise” orsimilar relative expressions are used, these only refer to the appendedfigures and not to an actual situation of use. The shown figures areschematic representations for which reason the configuration of thedifferent structures as well as there relative dimensions are intendedto serve illustrative purposes only.

In that context it may be convenient to define that the term “distalend” in the appended figures is meant to refer to the end of theinjection device carrying the injection needle whereas the term“proximal end” is meant to refer to the opposite end pointing away fromthe injection needle.

Elements having the same function in the different examples disclosedare preferably numbered with the same number carrying the number of theexample in the beginning. The piston rod is e.g. referred to as number120 in example one and as number 6120 in example six.

FIG. 1 discloses a user energized injection pen 1 comprising a housing10 and a cartridge holder 20. The housing 10 is provided with a window11 through which the dose set by rotating the push button 30 can beviewed. The cartridge holder 20 is at its distal end provided with athread 21 for securing a not shown injection needle to the injection pen1. The cartridge holder 20 is further provided with a longitudinalopening 22 through which a user can inspect the drug contained in thecartridge 40 embedded in the cartridge holder 20.

The interior of the injection pen is detailed disclosed in the FIGS. 2to 5.

The push button 30 is disposed at the proximal end of the injectiondevice 1 and connected to a dose setting member 50 by a plurality ofinwardly pointing locking protrusions 51 on the proximal end of the dosesetting member 50 entering depressions 31 in the proximal end of thepush button 30. This prevents rotation between the push button 30 andthe dose setting member 50. The two parts; push button 30 and dosesetting member 50 could be coupled together in a number of alternativeways e.g. through welding or gluing as long they are rotational lockedto each other.

The push button 30 can further be provided with a colour indication e.g.for indicating the type of insulin in the injection device 1. Suchcolour indication can be made as an insert in the push button 30.

A shield 60 is axially slidable mounted to the housing 10. The shield 60is provided with a protrusion 61 sliding in a longitudinal track 12provided on the inside surface of the housing 10. The shield 60 isthereby rotational locked to the housing 10 i.e. prevented from rotatingrelatively to the housing 10. The shield 60 is further provided with aplurality of radial shield teeth 62 at the proximal end which shieldteeth 62 interacts with a corresponding rim of push button slits 32thereby allowing the push button 30 to rotate relatively to the shield60 with a clicking sound. When axial pressure is applied to the pushbutton 30, the shield teeth 62 abut the ends of the push button slits 32thereby locking the push button 30 rotational to the shield 60.

The dose setting member 50 is at its distal end coupled to a drivesleeve 70. This drive sleeve 70 has on the outside surface a number ofhelical formed resilient arms 71 which at there connection points endsin toothed surfaces 72 pointing in the proximal direction. These toothedsurfaces 72 interacts with a dose setting member toothed rim 52 providedat the distal end of the dose setting member 50 when the dose settingmember 50 and the drive sleeve 70 is pressed together.

The dose setting member 50 further comprises a plurality of dose settingmember protrusions 53 which engage a toothed dose indication sleeve rim91 (best seen in FIG. 2) located at the proximal end of the doseindication sleeve 90. The dose setting member protrusions 53 can bebrought out of engagement with the toothed dose indication sleeve rim 91by moving the dose setting member 50 axially relatively to the doseindication sleeve 90 a distance determined by the size of the dosesetting member protrusions 53 and the toothed dose indication sleeve rim91. The dose setting member protrusion 53 are kept in engagement withthe toothed dose indication sleeve rim 91 by the resilient arms 71 onthe drive sleeve 70 which urges the dose setting member 50 in theproximal direction.

Further the dose indication sleeve 90 is provided with a number ofmounting openings 93 facilitating the insertion of the dose settingmember 50 in the dose indication sleeve 90 when assembling the injectiondevice 1.

At its distal end the dose indication sleeve 90 is provided with a malethread 92 engaging the female thread 101 of the thread member 100. Thisthread member 100 is centrally located in the housing 10 and rotationallocked to the housing 10 by a number of thread member protrusions 102engaging longitudinal tracks 12 provided on the inside surface of thehousing 10.

Internally the thread member 100 supports the piston rod guide 110. Thepiston rod guide 110 has a circular outer surface 111 supporting thethread member 100 and an outer threaded surface 112 engaging the drivesleeve 70 in its internal drive thread 73 (as best seen in FIG. 2).

The piston rod guide 110 has an internal thread 113 mating the thread122 on the piston rod 120.

The piston rod 120 which is centrally located in the housing 10 has acircular outer surface with a number of keys 121 and a thread 122. Apiston foot 123 for transferring pressure to a not shown resilientpiston inside the cartridge 40 is located at the distal end of thepiston rod 120.

A dish 130 is clicked into the distal end of the thread member 100. Thedish 130 has a centrally located keyed opening 131 mating the key 121 ofthe piston rod. Further the dish 130, as best seen in FIG. 3, has aplurality of inwardly pointing teeth 132 engaging the pawls 114 of thepiston rod guide 110 thereby securing that the piston rod guide 110 canonly rotate in one direction relatively to thread member 100 and thehousing 10. The allowed direction being one that moves the piston rod120 forward in the distal direction.

Rotation of the piston rod guide 110 and thereby the internal thread 113will screw the piston rod 120 forward through the dish 130 due to thefact that the dish 130 through its connection to the thread member 100is rotational locked to the housing 10

To set a dose, the dose setting member 50 is rotated by rotating thepush button 30 which is connected to the dose setting member 50. Thisrotating is transmitted to the scale indication sleeve 90 through theengagement between the dose setting member protrusions 53 and thetoothed dose indication sleeve rim 91.

During this rotation the scale indication sleeve 90 rotates up thethread 101 on the thread member 100. At the same time it moves the drivesleeve 70 in the proximal direction since the drive sleeve 70 rest onthe scale indication sleeve 90. The drive sleeve 70 is henceforthscrewed up the thread 112 on the piston rod guide 110.

The pitch on the threaded surface 112 of the piston rod guide 110 ispreferably different from the thread 101 on the thread member 100, andthe piston rod guide 110 preferably has the largest pitch.

If e.g. the ration between the pitches of the threaded surface 112 ofthe piston rod guide 110 and the thread 101 of the threaded member is 2to 1 with the pitch of the threaded surface of the piston rod guide 110being the largest. Then when e.g. rotating the dose indication sleeve 90four full revolutions up the thread 101 of the thread member 100, thedrive sleeve 70 will only be rotated two revolutions up the thread 112on the piston rod guide 112. This provides room for increasing thedistance between the not shown indications on the dose 25 indicationsleeve 90 while at the same time keeping the distance the push buttongrows out from the housing 10 at a minimum.

Upon rotation of the dose setting member 50 in the dose settingdirection, the shield 60 is moved axially out of the housing 10 as theshield 60 abuts the scale indication sleeve 90 and is guided in thetrack 12.

If the user wants to decrease the set dose, he rotates the dose settingmember 50 in the opposite direction whereby the dose indication sleeve90 is screwed down the thread 101 of the thread member 100.

The shield 60 is at least partially transparent such that the user cansee the indications printed on the outside surface of the scaleindication sleeve 90 through the shield 60. Since the shield 60 isaxially guided in the housing, the transparent part only needs to be thepart of the shield 60 passing past the window 11. Further instead ofbeing partly or fully transparent, the shield 60 could comprise alongitudinal opening through which the scale indication sleeve 90 can beviewed. The shield 60 needs not cover the scale drum in its entirelength. The shield 60 must however protect the part of the scaleindication sleeve 90 that is outside the boundaries of the housing (10)when the set dose is injected such that the user does not apply asideways pressure on the scale indication drum 90 when it rotates backto its initial position.

To inject a dose, the dose setting member 50 is moved in distaldirection by pressing the push button 30 back towards the housing 10.Such axial movement locks the push button 30 to the shield 60 and itmoves the dose setting member protrusions 53 out of engagement with thetoothed dose indication sleeve rim 91 thereby allowing the doseindication sleeve 90 to rotate down the thread 101 on the threadedmember 100. At the same time the dose setting member 50 presses theresilient arms 71 down and abuts the toothed surface 52 which rotationallocks the dose setting member 50 to the drive sleeve 70.

In this position continuously forward axial movement of the dose settingmember 50 and the drive sleeve 70 forces the piston rod guide 110 torotate due to the engagement between the internal drive thread 73 andthe thread 112 of the piston rod guide 110 thereby rotating the pistonrod guide 110 and screwing forward the piston rod 120.

End-of-Content Feature

A nut 80 is located over the dose setting member 50 and is in threadedcontact with an exterior thread 54 on the dose setting member 50 throughan internal thread 81. The nut 80 is at the same time inrotatableconnected to the shield 60 by the protrusion 82 being guided in thelongitudinal slot 63 located on the inside of the shield 60.

When a dose is set the dose setting member 50 is rotated relatively tothe shield 60 and to the nut 80 bringing the nut 80 forward in thedistal direction from a proximal starting point. The distance the nut 80is brought forward relates to the size of dose being set.

When the set dose is injected, the nut 80 is moved axially forward thesame distance as the dose setting member 50 and the shield 60. Theposition of the nut 80 on the exterior thread 54 therefore relates tothe remaining content of drug in the reservoir.

When the nut 80 reaches the end of the thread 54, the nut 80 can bescrewed no further and the dose setting member 50 in prohibited fromfurther rotation. A more detailed description of such end-of-dosefeature is provided in WO 01/019434 which is hereby incorporated byreference.

When the thread 54 is provided on the part that rotates with the slowestrotational speed which in this case is the dose setting member 50, thelength of the thread 54 can be reduced since the nut 80 only moves alittle distance in the thread 54. This is illustrated in the embodimentdepictured in FIG. 9.

Further the end of the thread 54 can be made with a pitch different fromthe remaining part of the thread 54. If the thread is e.g. made largerin the end on the thread 54, the nut can be accelerated in the end ofits run which could make room for a larger end surface in the thread 54.

Embodiment Disclosed in FIG. 6 to 8

The push button 230 is firmly connected to a click element 2150 thatfollows the movement of the push button 230.

This click element 2150 is provided with resilient arms 2151 thatengages a toothed ring 264 in the shield 260. Further a toothed ring2152 engages a rim of teeth 291 on the dose indication sleeve 290.

The shield 260 is provided with a protrusion 261 guided in alongitudinal track 212 inside the housing 210.

Further the piston rod 2120 is provided with two threads 2122, 2124having different pitches and where the distal thread 2122 has a keyedsurface 2121 mating the key 2141 in the key element 2140. The distalthread 2122 mates the internal thread 2133 of a dish 2130 which issecured in the cartridge holder 220.

Whenever the piston rod 2120 is rotated it is screwed forward in thethread 2133. At the same time the key element 2140 secures that thepiston rod 2120 can only rotate in one rotational direction due to theengagement between the resilient arms 2142 and the and an internaltoothed ring 2103 provided on the thread member 2100 which isnon-rotational fixed in the housing 210.

The proximal thread 2124 mates the internal thread 273 of the drivesleeve 270 which further has a single ring shaped track 274 engaging aninner ring shaped protrusion 294 on the dose indication sleeve 290 suchthat the drive sleeve 270 and the scale indication sleeve 290 axiallymoves together.

When setting a dose, the user rotates the push button 230. Due to theengagement between the protrusions 291 and the toothed ring 2152, thescale indication sleeve 290 follows the rotation of push button 230. Indoing so, the scale indication sleeve 290 is by its inside thread 292rotated up the thread 2101 on the thread member 2100.

The engagement between the ring shaped track 274 of the drive sleeve 270and the inner ring shaped protrusion 294 of the scale indication sleeve290 forces the drive sleeve 270 to follow the axial movement of thescale indication sleeve 290. During its axial movement, the drive sleeve270 rotates on the thread 2124 which has a pitch different from thepitch of the thread 2101 such that the rotational speed of the drivesleeve 270 on one hand and the scale indication sleeve 290 and the pushbutton 230 on the other hand are different.

The scale indication sleeve 290 is provided with an outer ring 295 onwhich the proximal end of the shield 260 rests such that the shield 260is moved away from the injection device 201 when the drive sleeve 270and the scale indication sleeve 290 is rotated.

In order to inject a dose, the user presses back the push button 230against the force of the spring 277 whereby the teeth 233 on the pushbutton 230 engages the teeth 265 at the proximal end of the shield 260inrotatable locking the shield 260 and the push button 230 together. Atthe same time the drive sleeve 270 and the push button 230 is keptinrotatable by a ring of not shown teeth on the click element 2150entering into engagement with a ring of corresponding teeth 276 on thedrive sleeve 270.

The toothed ring 2152 on the click element 2150 moves out of engagementwith the protrusions 291 on the dose indication sleeve 290 whereby thesleeve 290 is free to rotate. When the toothed ring 2152 is out ofengagement with the protrusion 291 and further force is applied theaxial forward movement of the drive sleeve 270 forces the piston rod2120 to rotate as well as the dose indication sleeve 290 is also forcedto rotate in its thread connection 2101, 292. The rotation of the pistonrod 2120 screws the piston rod 2120 forward in the mating thread 2133 ofthe dish 2130.

A not shown EOC nut engages the longitudinal track 2104 in the threadmember 2100 and the helical track 275 of the drive sleeve 270.

Embodiment Disclosed in FIG. 9 to 11

In this embodiment a dose is set by rotating the push button 330 whichrotates the click element 3150. Due to engagement between the rim ofteeth 3152 on the click element 3150 and the rim of teeth 391 on theinside surface of the dose indication sleeve 390 this is rotated withthe push button 330.

The internal thread 392 is screwed up the thread 3101 provided on thethread member 3100 such that the dose indication sleeve 290 is liftedout from the housing 310. Due to the engagement between the rim 394inside the dose indication sleeve 290 and the rim 378 on the drivesleeve 370, the drive sleeve 370 is also lifted in the proximaldirection. During this axial movement of the drive sleeve 370 it isrotated on the thread 3112 provided on the piston rod guide 3110.

The thread member 3100 is locked to the housing 310 and the piston rodguide 3110 is coupled to the thread member 3100 via a one way couplingbetween the resilient pawls 3114 on the piston rod guide 3110 and thetoothed ring 3132 inside the distal end of the thread member 3100.

When injecting the set dose, the user presses the push button 330axially back towards the housing 310 against the force of the spring377.

The push button 330 and the click member 3150 locks to the shield 360which is guided in a longitudinal recess 312 in the housing 310. Furtherthe drive sleeve 370 locks to the click member 3150 via the teeth 376 onthe rim 378 engaging a rim of not shown teeth located distally on theclick element 3150. This results in an axial movement of the push button330, the click element 3150, the drive sleeve 370 and the shield 360.

The axial returning of the drive sleeve 370 forces the piston rod guide110 to rotate due to the thread connection 3112, 373. The internalthread 3113 of the piston rod guide 3110 transforms rotation to thepiston rod 3120 which is screwed forward in the keyed engagement withthe dish 3130.

At the same time the teeth 3152 on the click element 3150 escapes theengagement with the protrusions 391 on the dose indication sleeve 390which is then screwed down the thread 3101 on the thread member 3100back to its zero position.

An End-of-Content nut 380 is provided between the drive sleeve 370 andthe thread member 3100.

Embodiment Disclosed in FIG. 12-13

In this embodiment the dose is set by rotating the dose setting member550. The dose setting member 550 has internal teeth 553 engaging sleeverim 591 on the dose indicator sleeve 590. In the disclosed embodiment,the dose indication sleeve 590 is made up from two different parts whichduring assembly is connected in to one functional element. This elementcould however also be produced as one moulded element.

Once the user rotates the dose setting member 550, the dose indicationsleeve 590 is lifted in the proximal direction by the thread 5101 on thethread member 5100 which is secured in the housing 510. During thisproximal movement, the driver 570 will be lifted in the proximal duringas it stands on the dose indication sleeve 590. The driver 570 has aninternal thread 573 engaging the outwardly pointing thread 5112 on thepiston rod guide 5110 and is thus forced to rotate on this thread 5112when moved in the proximal direction. This thread 5112 has a pitchdifferent from the pitch of the thread 5101 on the thread member 5100accomplishing a gearing between the axial movement of the doseindication sleeve 590 and the driver 570.

When injecting the set dose, the user applies a pressure on the pushbutton 530 which is secured in the dose setting member 550. This movesthe dose setting member 550 axially in the distal direction thusreleasing the teeth 553 from the toothed rim 591. The same axialmovement also moves the teeth 552 on the dose setting member 550 intoengagement with the proximal teeth 576 on the driver 570 which is biasedaway from the push button 530 by the spring element 577.

The dose setting member 550 locks to the shield 560 through the teethconnection 555/565. Since the shield 560 is guided in the track 512 inthe housing 510, continuously movement of the dose setting member 550 inthe distal direction will force the driver 570 axially forward. Thisaxial forward movement of the driver 570 forces the piston rod guide5110 to rotate in the thread connection 5112/573 between the driver 570and the piston rod guide 5110.

The dose indication sleeve 590 is released from the dose setting member550 as the teeth 553 moves free of the toothed rim 591. The doseindication sleeve 590 is therefore free to return to its zero positiondown the thread 5101 as it is forced in the distal direction by thecontinuous pressure on the push button 530.

At the end of stroke, the dose indication sleeve 590 is accelerated dueto the fact that the thread 5101 on the thread member 5100 has a higherpitch on the last revolution. This acceleration can be felt by the userwho is thus informed that the mechanism has reached the end of thedosing stroke.

Embodiment Disclosed in FIG. 14

If the two threads 5112, 5101 has different directions as disclosed inFIG. 14, the mechanism works in one direction when setting a dose and inthe opposite direction when expelling the set dose.

Embodiment Disclosed in FIG. 15-16

In the embodiment disclosed in FIG. 15-16 a dose is set by rotating thepush button 630 which is connected to a transparent shield 660 such thatthe shield 660 rotates together with the push button 630. The shield 660and the push button 630 could even be moulded as to form one common dosesetting member.

The internal teeth 665 on the shield 660 engage the toothed rim 691 onthe dose indicator sleeve 690 such that this sleeve 690 rotates togetherwith the shield 660. During this rotation, the dose indication sleeve690 is guided in the thread 6101 on the thread member 6100 which issecured in the housing 610.

The thread member 6100 has an additional thread 6105 in which theinternal drive thread 673 of the driver 670 is guided as it is pulled inthe proximal direction by the dose indication sleeve 690. Thisadditional thread 6105 preferably has a pitch different form the pitchof the thread 6101 in which the dose indication sleeve 690 is guidedsuch that a gearing between the scale indication sleeve 690 and thedriver 670 is obtained.

In order to inject the set dose, the user applies a pressure on the pushbutton 630. This pressure moves the push button 630 and the shield 660in the distal direction thus releasing the teeth 665 on the shield 660from the toothed ring 691 thereby releasing the dose indication sleeve690 from the shield 660. At the same time the teeth 6161 on theconnector pipe 6160 enters into engagement with the teeth 676 on thedriver 670. As continuously pressure is applied to the push button 630,the driver 670 rotates down the thread 6105 on the thread member 6100.Since the connector pipe 6160 is now connected to the driver 670, theconnector pipe 6160 also rotates. This rotation is through theconnection between the internal protrusion 6162 on the connector pipe6160 and the longitudinal track 6115 in the piston rod guide 6110transformed to a rotation of the piston rod 6120 which is screwedforward in the internal thread 2133 in the dish or nut 2130.

This embodiment also discloses an End-of-Content indicator providing theuser with a tactile indication once the end of the dosing stroke isreached. The mechanism comprises and EoD accelerator that is moved awayfrom the proximal end of the piston rod guide 6110 as the dose is set.When the dose is injected, the EoD accelerator 6170 is moved towards theproximal end of the piston rod guide 6110. As it reaches the piston rodguide 6110, it is pressed radially outwardly by the piston rod guide6110 due to the pressure applied to the push button 630. This is felt bythe user as an increase in the pressure necessary. Once the EoDaccelerator snaps over the end of the piston rod guide 6110, the userfeels an decrease in the pressure necessary. This sudden decrease alsoaccelerates the driver 670 which provides a distinct sound as the driver670 accelerates into the dose indication sleeve 690 at its distal end.

Embodiment Disclosed in FIG. 17

If the two threads 6101, 6105 has different directions as disclosed inFIG. 17, the mechanism works in one direction when setting a dose and inthe opposite direction when expelling the set dose.

Some preferred embodiments have been shown in the foregoing, but itshould be stressed that the invention is not limited to these, but maybe embodied in other ways within the subject matter defined in thefollowing claims.

List of Part:

FIG. FIG. FIG. FIG. FIG. 1-5 6-8 9-11 12-14 15-17 1 201 301 InjectionPen 10 210 310 510 610 Housing 11 Window 12 212 512 Longitudinal Track20 220 320 Cartridge Holder 21 Thread 22 Opening 30 230 330 630 PushButton 31 Depression 32 Push Button Slits 233 Push Button Teeth 40 240340 540 640 Cartridge 50 550 Dose Setting Member 51 Locking Protrusion52 552 Toothed Rim 53 553 Dose Setting Member Protrusions 54 EOC Thread555 Teeth 60 260 360 660 Shield 61 261 Protrusion 62 Radial ShieldsTeeth 63 Longitudinal Slot 264 Toothed ring 265 565 665 Teeth 70 270 370570 670 Driver 71 Resilient Arms 72 Toothed Surface 73 273 573 InternalDrive Thread 274 Ring Shaped Track 275 Helical Thread 276 376 576 Teeth277 377 577 Spring 378 Rim 80 380 EOC Nut 81 Internal Thread 82Protrusion 90 290 390 590 690 Dose Indication Sleeve 91 291 391 591 691Dose Indication Sleeve Rim 92 392 Interior Thread 93 Mounting Opening294 Inner Ring Shaped Protrusion 295 Outer Ring Shaped Protrusion 1002100 3100 5100 6100 Thread Member 101 2101 3101 5101 6101 Thread 102Thread Member Protrusion 2103 Toothed Ring 2104 Longitudinal Track 6105Additional Thread 110 3110 5110 6110 Piston Rod Guide 111 Outer Surface112 5112 Thread 113 Internal Thread 114 Pawls 120 2120 3120 6120 PistonRod 121 2121 Key 122 Piston Rod Thread 123 Piston Foot 2124 ProximalThread 130 2130 3130 6130 Dish 131 Keyed Opening 132 3132 InwardlyPointing Teeth 2133 6133 Internal Thread 2140 Key Element 2141 Key 2142Resilient Arm 2150 3150 Click Element 2151 Resilient Arm 2152 3152Toothed Ring 6160 Connector Pipe 6161 Teeth 6162 Internal Protrusion6170 EoD Accelerator

1. An injection device for apportioning set doses of a drug from areservoir comprising: A housing (10, 210, 310, 510, 610) adapted to holdthe reservoir (40, 240, 340, 540, 640), A dose setting member (30, 50,230, 2150, 330, 3150, 550, 630, 660) for setting the size of the dose tobe expelled, A scale indication sleeve (90, 290, 390, 590, 690) forindicating the size of the set dose, A piston rod (120, 2120, 3120,5120, 6120) for activating the reservoir (40, 240, 340, 540, 640) toexpel the set dose, A drive sleeve (70, 270, 370, 570, 670) operationalassociated with the piston rod (120, 2120, 3120, 5120, 6120) for drivingthe piston rod (120, 2120, 3120, 5120, 6120) forward, characterized inthat, the dose indication sleeve (90, 290, 390, 590, 690) is surroundedby a shield (60, 260, 360, 560, 660) through which the scale indicationsleeve (90, 290, 390, 590, 690) is visible.
 2. An injection deviceaccording to claim 1, characterized in that, the shield (60, 260, 360,560, 660) is an at least partly transparent hollow cylinder-shapedsleeve surrounding at least the major part of the drive sleeve (70, 270,370, 570, 670) and the dose indication sleeve (90, 290, 390, 590, 690).3. An injection device according to claim 2, characterized in that, thedrive sleeve (70, 270, 370, 570, 670) is rotational locked to the shield(60, 260, 360, 560, 660) at least when the set dose is expelled.
 4. Aninjection device according to claim 1, characterized in that, the shield(660) and the push button (630) is rotational locked to each other. 5.An injection device according to claim 1, characterized in that, theshield (60, 260, 360, 560, 660) is axially and non-rotatable guided inthe housing (10, 210, 310, 510, 610) by a protrusion (61, 261) on theshield engaging a longitudinal track (12, 212, 312) in the housing (10,210, 310, 510, 610).
 6. An injection device for apportioning set dosesof a drug from a reservoir (40, 240, 340), comprising: a housing (10,210, 310, 510, 610) adapted to hold a reservoir (40,240, 340, 540, 640),a dose setting member (30, 50; 230, 2150; 330, 3150; 550; 630, 660) forsetting the size of the dose to be expelled, a scale indication sleeve(90, 290, 390, 590, 690) for indicating the size of the set dose, apiston rod (120, 2120, 3120, 5120, 6120) for activating the reservoir(40, 240, 340, 540, 640) to expel the set dose, a drive sleeve (70, 270,370, 570, 670) operational associated with the piston rod (120, 2120,3120, 5120, 6120) for driving the piston rod (120, 2120, 3120, 5120,6120) forward, characterized in that, the drive sleeve (70, 270, 370,570, 670) is associated with a first thread (112, 2120, 3112, 5112,6105) and releasable connected to the dose setting member (30, 50; 230,2150; 330, 3150; 550; 630, 660), and the dose indication sleeve (90,290, 390, 590, 690) is associated with a second thread (101, 2101, 3101,5101, 6101), and releasable connected to the dose setting member (30,50; 230, 2150; 330, 3150; 550; 630, 660), wherein the first thread (112,2120, 3112, 5112, 6105) has a pitch different from the pitch of thesecond thread (101, 2101, 3101, 5101, 6101).
 7. An injection deviceaccording to claim 1, characterized in that, the dose setting member(30, 50; 230, 2150; 330, 3150; 550; 630, 660) is disconnected from thedrive sleeve (70, 270, 370, 570, 670) and connected to the doseindicating sleeve (90, 290, 390, 590, 690) when setting a dose, and thatthe dose setting member (30, 50; 230, 2150; 330, 3150; 550; 630, 660) isconnected to the drive sleeve (70, 270, 370, 570, 670) and disconnectedfrom the dose indicating sleeve (90, 290, 390, 590, 690) when the setdose is expelled.
 8. An injection device according to claim 1,characterized in that, the pitch of the first thread (112, 2120, 3112,5112, 6105) is larger than the pitch of the second thread (101, 2101,3101, 5101, 6101).
 9. An injection device according to claim 3,characterized in that, the drive sleeve (70, 270, 370, 570, 670) isprevented from rotating in relation to the housing (10, 210, 310, 510,610) when the set dose is expelled.
 10. An injection device according toclaim 4, characterized in that, the drive sleeve (70, 270, 370, 570,670) is coupled to the housing (10, 210, 310, 510, 610) through a shield(60, 260, 360, 560, 660) which is non-rotatable guided in the housing(10, 210, 310, 510, 610).
 11. An injection device according to claim 5,characterized in that, the shield (60, 260, 360, 560, 660) is at leastpartly transparent.
 12. An injection device according to claim 1,characterized in that, the drive sleeve (70, 270, 370, 570, 670) isaxially connected to the scale indication sleeve (90, 290, 390, 590,690) to follow axial movement of the scale indication sleeve (90, 290,390, 590, 690) at least when the size of the dose is set.
 13. Aninjection device according to claim 1, characterized in that the firstthread (112, 3112, 5112) engaged by the drive sleeve (70, 370, 570) isprovided on a piston rod guide (110, 3110, 5110) rotating the piston rod(120, 3120, 5120)
 14. An injection device according to claim 1,characterized in that the first thread (2124) engaged by the drivesleeve (270) is provided on the piston rod (2120).
 15. An injectiondevice according to claim 1, characterized in that, the second thread(101, 2101, 3101, 5101, 6101) engaged by the dose indication sleeve (90,290, 390, 590, 690) is provided on a thread tower (100, 2100, 3100,5100, 6100) centrally located in the housing (10, 210, 310, 510, 610)and non-rotatable connected to the housing (10, 210, 310, 510,610).